Field of Invention
The present invention relates to a silty floating mud collection device of coastal engineering, and more specifically belongs to the field of sampling and testing technologies.
Description of Related Arts
Exploitation of nautical depth resources is: navigating by using a floating mud layer below a current water depth in a silty port area waterway and a coastal waterway having a silt property, which not only can increase a navigable depth, but also can reduce maintenance costs for the navigable depth, prolong a maintenance dredging period for ports, waterways and berths, and improve port economic benefits. Since the 80s of the 20th century, China began to develop and apply the nautical depth at some ports, and released a Ministry of Communications industry standard “Silty Seaport Nautical Depth Application Technology Specification” (JTJ/T325-2006), which is then enforced as a formal standard in China. To determine characteristics of a nautical floating mud layer thickness, it is needed to collect floating mud samples of different layers in an underwater back-silting layer, and to perform tests of particle composition analysis, sediment settling, density, silt rheological behavior, and the like. At present, a great progress has been made both in China and abroad in design and manufacture of a undisturbed soil sampler, and the representatives are: a fixed piston thin-wall soil sampler, single-rotary three (two)-barrel soil sampler, and the like, which all have relatively high soil sampling performance, and basically meet requirements of engineering geological survey. However, they are applied to stratum such as soft clay, sand gravel, and differentiated rock; because the floating mud layer involved in the nautical depth has an excessively high water content, so that the floating mud is in a flowing state. Obviously, the foregoing soil samplers cannot be applied to collect floating mud in a flowing state in different depths. In addition, the foregoing soil samplers use a direct pressing, hammer pressing or pressure rotating sampling manner, which cannot be applied to collect the floating mud either.
Because some sampling devices are of an opening manner, quality of samples will be affected by a lifting process, and deeper water indicates a larger impact.
For example, in China utility model patent 201020513399.0, a middle locking soil sampler is disclosed, which has a tubular structure and includes three parts: an upper soil sampling tube, a middle locking device, and a lower soil sampling tube. The upper soil sampling tube is connected to the middle locking device, the middle locking device is formed by a shaft valve seat and a shaft valve, the shaft valve is embedded in the shaft valve seat; the middle locking device is connected to the lower soil sampling tube; the upper soil sampling tube is a soil sampling inner tube, and an outer brake tube is installed at the outside of the upper soil sampling tube; a lower end portion of the outer brake tube has a vertical guide groove and an arc-shaped brake groove, the guide groove makes a suspension body move up and down only in a vertical direction, and the arc-shaped brake groove makes the shaft valve rotate only in a horizontal axial direction. Opening of the middle shaft valve depends on reaction of friction formed by soil and side wall of device, however reaction of a floating mud layer in a flowing state is very slight, which affects the opening, and therefore a sampling rate is reduced.
For another example, in China utility model patent 201220330329.0, a tooth-type sampler closing device is disclosed. The closing device includes a clasp guide rod, a retractable damping fin, a barrel body, and a tooth-type closing piece; the clasp guide rod is fixed at a lower end of a soil sampler, the clasp guide rod is mechanically connected to the barrel body in a sliding manner, an upper end of the barrel body is provided with the retractable damping fin, and a lower end of the barrel body is connected to the tooth-type closing piece by using a spring. When the soil sampler is drawn out, the damping fin is opened by using resistance of the mud, the barrel body moves down, and the closing piece closes the soil sample.
For still another example, in China utility model patent 201220330330.3, a backstop closed soil sampler is disclosed, which includes a piston, a soil sample tube, a backstop closing tube, and a movable shoe. The piston is sequentially connected to the soil sample tube, the backstop closing tube and the movable shoe; the piston, the soil sample tube and the backstop closing tube are fixedly connected together; the movable shoe is mechanically connected to the backstop closing tube in a sliding manner, and a backstop piece triggered by the movable shoe is installed inside the backstop closing tube. When the soil sampler is drawn out, the movable shoe will slide down by resistance of the mud, and then drive the backstop piece to close the soil sample.
Although all the foregoing three soil samplers may be applied to collecting underwater silty floating mud, but there are limitations. The first soil sampler is applicable to sampling when the surface of a river bed is in a soft plastic or plastic state. The second and the third soil samplers have the following problems: There are relatively large differences existing in water content, specific gravity, density, sand grain content of floating, flowing and silty mud, and soft or plastic soil, which form different friction; friction of floating and flowing mud is the smallest, and a high sampling rate cannot be achieved while a closing piece of the soil sampler is closed by control of friction. In addition, a lower-part structure of the first soil sampler uses vacuum negative pressure sampling, which is universally used in current survey technologies and is applicable to sampling of soft or plastic soil with a shape; the second and the third soil samplers use a closing device, which is an improvement for successively collecting floating mud, but the closing device is formed by backstop (closing) pieces, factors such as synchronous closing of the closing pieces and space between closing pieces all cause leaking of water in floating mud with high water content, and therefore affect accuracy of sample data.
Moreover, a sample upper opening cover during sample collecting is not considered in the prior art, and undisturbed state of the entire sample cannot be ensured.